I just recently took out my mirena a few days short of a month ago after having it in for 7 years?

Changed it out at year 7, I haven't got my period yet. We would like to try and get pregnant but my doctor said we should use protection until I have a period because there is risk for miscarriage?! I called the office and told them I didn't get my period yet, was it normal, and she said it could take up to 3 months to regulate? We do not want to wait that long, any suggestions please? TIA